Portion of a display screen with a user interface



FIG. 1 is a front view of a portion of a display screen with a user interface showing the claimed design in accordance with a first embodiment; and,

FIG. 2 is a front view of a portion of a display screen with a user interface showing the claimed design in accordance with a second embodiment.

The portion of the display screen and the portions of the user interface illustrated in broken lines form no part of the claimed design. 

The ornamental design for a portion of a display screen with a user interface, as shown and described. 